standard engineering techniques; however, the nature of the material 

 sometimes required deviations from accepted procedures. 



Original water content . The original water content of the soil 

 mass , defined as the weight of water in a portion of sample divided 

 by the weight of solids in that portion, was established by oven-drying 

 approximately 50 grams (dry weight) of sample at 105 degrees Celsius 

 for approximately 24 hours. The 50-gram sample was selected from 

 the 10-centimeter sediment section after the section had been 

 thoroughly mixed. 



Grain size distribution . The results of a sieve and hydrometer 

 analysis were used to determine the sample's grain size distribution. 

 The test procedure involved mixing 50 grams (dry weight) of sample 

 from the sediment section with an electric mixer. During the mixing, 

 125 milliliters of diluted sodium pyrosphosphate were added to 

 deflocculate the soil. After the slurry was mixed for approximately 



1 minute, the contents were added to a 1 ,000-milliliter hydrometer 

 jar. The hydrometer jar was then filled with distilled water and left 

 overnight in a water bath at 20 degrees Celsius. The remainder of 



the hydrometer test followed standard American Society for Testing 

 and Materials (ASTM, 1964) procedures. After the 24-hour hydrometer 

 reading, the entire sample in the hydrometer was washed through a 

 Number 325 sieve and was dried for 2 hours at 105 degrees Celsius, 

 after which the material was shaken through a nest of sieves. A 

 representative portion of the material coarser than the 325 sieve 

 was saved. The Bureau of Soils Classification System was used to 

 distinguish between sands, silts, and clays. This classification 

 system considers the particle a sand if the grain size is between 



2 and 0.05 millimeters, a silt if the grain size is between 0.05 and 

 0.005 millimeter, and a clay if the particle is smaller than 



0.005 millimeter. 



Carbonate-organic carbon content . The carbonate carbon and 

 organic carbon contents of the samples were determined by utilizing 

 a Leco induction furnace. The furnace measured the amount of carbon 

 released during the combustion of two samples from a given increment. 

 One sample was treated with hydrochloric acid to remove the carbonate 

 carbon content, while the second sample was left untreated. The 

 treated sample thus included the carbon from the organic matter only, 

 and the untreated sample measured carbon from both. By subtracting 

 one from the other, the amount of carbon lost during the reaction 

 with the hydrochloric acid was defined; this amount was the carbon 

 content from the carbonate source only. Since only the carbon was 

 measured, instead of whole molecules of organic matter or carbonate 

 which contain other elements, the organic carbon and carbonate 

 carbon results reported should be multiplied by factors of 8.33 

 and 1.7, respectively, in order to obtain the weight percentages of 

 the compounds. 



